151 lines
4.5 KiB
ReStructuredText
151 lines
4.5 KiB
ReStructuredText
.. index:: pair\_style lj/expand
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pair\_style lj/expand command
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=============================
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pair\_style lj/expand/gpu command
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=================================
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pair\_style lj/expand/kk command
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================================
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pair\_style lj/expand/omp command
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=================================
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pair\_style lj/expand/coul/long command
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=======================================
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pair\_style lj/expand/coul/long/gpu command
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===========================================
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Syntax
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""""""
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.. parsed-literal::
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pair_style lj/expand cutoff
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* cutoff = global cutoff for lj/expand interactions (distance units)
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Examples
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""""""""
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.. parsed-literal::
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pair_style lj/expand 2.5
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pair_coeff \* \* 1.0 1.0 0.5
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pair_coeff 1 1 1.0 1.0 -0.2 2.0
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pair_style lj/expand/coul/long 2.5
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pair_style lj/expand/coul/long 2.5 4.0
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pair_coeff \* \* 1.0 1.0 0.5
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pair_coeff 1 1 1.0 1.0 -0.2 3.0
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Description
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"""""""""""
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Style *lj/expand* computes a LJ interaction with a distance shifted by
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delta which can be useful when particles are of different sizes, since
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it is different that using different sigma values in a standard LJ
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formula:
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.. image:: Eqs/pair_lj_expand.jpg
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:align: center
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Rc is the cutoff which does not include the delta distance. I.e. the
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actual force cutoff is the sum of cutoff + delta.
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For all of the *lj/expand* pair styles, the following coefficients must
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be defined for each pair of atoms types via the
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:doc:`pair\_coeff <pair_coeff>` command as in the examples above, or in
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the data file or restart files read by the :doc:`read\_data <read_data>`
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or :doc:`read\_restart <read_restart>` commands, or by mixing as
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described below:
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* epsilon (energy units)
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* sigma (distance units)
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* delta (distance units)
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* cutoff (distance units)
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The delta values can be positive or negative. The last coefficient is
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optional. If not specified, the global LJ cutoff is used.
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For *lj/expand/coul/long* only the LJ cutoff can be specified since a
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Coulombic cutoff cannot be specified for an individual I,J type pair.
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All type pairs use the same global Coulombic cutoff specified in the
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pair\_style command.
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----------
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Styles with a *gpu*\ , *intel*\ , *kk*\ , *omp*\ , or *opt* suffix are
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functionally the same as the corresponding style without the suffix.
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They have been optimized to run faster, depending on your available
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hardware, as discussed on the :doc:`Speed packages <Speed_packages>` doc
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page. The accelerated styles take the same arguments and should
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produce the same results, except for round-off and precision issues.
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These accelerated styles are part of the GPU, USER-INTEL, KOKKOS,
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USER-OMP and OPT packages, respectively. They are only enabled if
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LAMMPS was built with those packages. See the :doc:`Build package <Build_package>` doc page for more info.
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You can specify the accelerated styles explicitly in your input script
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by including their suffix, or you can use the :doc:`-suffix command-line switch <Run_options>` when you invoke LAMMPS, or you can use the
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:doc:`suffix <suffix>` command in your input script.
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See the :doc:`Speed packages <Speed_packages>` doc page for more
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instructions on how to use the accelerated styles effectively.
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----------
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**Mixing, shift, table, tail correction, restart, rRESPA info**\ :
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For atom type pairs I,J and I != J, the epsilon, sigma, and shift
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coefficients and cutoff distance for this pair style can be mixed.
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Shift is always mixed via an *arithmetic* rule. The other
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coefficients are mixed according to the pair\_modify mix value. The
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default mix value is *geometric*\ . See the "pair\_modify" command for
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details.
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This pair style supports the :doc:`pair\_modify <pair_modify>` shift
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option for the energy of the pair interaction.
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The :doc:`pair\_modify <pair_modify>` table option is not relevant
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for this pair style.
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This pair style supports the :doc:`pair\_modify <pair_modify>` tail
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option for adding a long-range tail correction to the energy and
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pressure of the pair interaction.
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This pair style writes its information to :doc:`binary restart files <restart>`, so pair\_style and pair\_coeff commands do not need
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to be specified in an input script that reads a restart file.
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This pair style can only be used via the *pair* keyword of the
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:doc:`run\_style respa <run_style>` command. It does not support the
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*inner*\ , *middle*\ , *outer* keywords.
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----------
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Restrictions
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""""""""""""
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none
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Related commands
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""""""""""""""""
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:doc:`pair\_coeff <pair_coeff>`
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**Default:** none
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.. _lws: http://lammps.sandia.gov
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.. _ld: Manual.html
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.. _lc: Commands_all.html
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